AM50 Magnesium Alloy Research Articles

Effect of Adding Rare Earth Elements Er and Gd on the Corrosion Residual Strength of Magnesium Alloy

Abstract The effects of the single and compound addition of rare earth Gd and Er on corrosion resistance and residual strength of as-cast AM50 magnesium alloy were studied using XRD, SEM, EDS, the weightlessness test, electrochemistry method, and tensile test. The results of XRD and SEM showed that Al3Er, Al2Gd3, and Al–Mn–Gd(Er) phases appeared in the alloy structure after the addition of rare earth Er and Gd. The results from the weightlessness test and Tafel curves show that the corrosion resistance of the modified composite rare earth was improved. Stress concentration caused by a corrosion pit is the direct cause of the tensile samples after corrosion. The corrosion residual strength of modified composite rare earth specimens is better than that of modified single rare earth samples. Fracture analysis indicates that the addition of rare earth elements did not change the fracture mechanism of the alloy, and the fracture was still the cleavage fracture.

A crystal-plasticity model of extruded AM30 magnesium alloy

An enhanced crystal-plasticity finite-element model is developed to model the effects of texture, grain size and loading direction on asymmetrical tension-compression behaviour of AM30 magnesium alloy. A constitutive description of plastic deformation in the suggested scheme accounts for contributions from deformation slip and twinning. The calibrated model was employed to investigate the effects of texture and grain size on the yield stress and strain-hardening behaviour of AM30 magnesium alloy at room temperatures under various loading conditions. The study reveals that grain refinement and initial texture significantly influence the mechanical behaviour of AM30. Results show that the key factor controlling the tension-compression asymmetry is deformation twinning. Two techniques, which could be used to reduce this asymmetry, are grain refinement and weakening of the initial texture in extruded AM30.

Mixed-mode fracture behavior of AM60 magnesium alloy using two parameter fracture mechanics

The main objective of this study is the precise estimation of the fracture parameters by applying crack-tip constraint under mixed-mode loading conditions. To this aim, an AM60 magnesium alloy with elastic-plastic behavior has been utilized. Fracture tests were conducted using a modified version of Arcan device in mode-I, 45° mixed-mode, and mode-II loading conditions. Different initial crack lengths were used to create a wide range of crack-tip constraints. In addition, experiments have been carried out at different temperatures to enhance the applicability and effectiveness of research in real applications. Using finite element analysis (FEA), the crack-tip constraint, Q, corresponding to the laboratory conditions was extracted. The results show a strong dependency of Q constraint on the loading angle so that by changing the loading angle from mode-I to mode-II, the crack-tip constraint experienced a significant increasing trend, while the dependency on the crack length and temperature is negligible. Finally, the J-Q curves are presented for different temperatures and the corresponding relations are used for predicting the critical values of the J-integral in a specific condition and the obtained results are compared with the experimental results. According to the results, the minimum and maximum differences between the obtained results from the relations and the experimental result are 0.01% and 19.49%, respectively. Moreover, the J-R resistance curve has been modified using the crack-tip constraint. Regarding the obtained results, the minimum and maximum differences between the extracted values and the experimental results were 15.76% and 17.66% respectively. It can be concluded that using the results of this research eliminates the need for conducting the corresponding experimental tests, and the critical values of the J-integral can be obtained with reasonable accuracy by calculating the crack-tip constraint through FEA.

Effect of Lubricant and Operation Temperature on the Metallurgical Property of AM60 Magnesium Alloy in ECAP Process

In this study, the effect of the lubricant type and operating temperature on the process of equal channel angular pressing (ECAP) for magnesium alloy AM60 was investigated. For this purpose, designed experiments were conducted in a rounded cavity die with a channel angle of 90° at three different operating temperatures using two lubricants including graphite and molybdenum disulfide. Then, the apparent qualities, microhardness, microstructure of the samples, and variation in the process force were analyzed. Findings revealed that using the molybdenum disulfide as a lubricant at high temperature reduces damage to the workpiece and the process force. However, the ECAP process increases the hardness of the processed samples and the hardness is almost the same in different modes of lubrication. Moreover, at lower temperatures, the hardness of the samples is higher. The microstructure of the samples demonstrated that molybdenum disulfide lubricant leads to finer grain size and a higher level of alignment than lubrication using graphite. At higher temperatures, dynamic recrystallization occurs during deformation, leading to the formation of ultrafine equiaxed grains in some regions of the microstructure.

High strength AM50 magnesium alloy as a material for possible stent application in medicine

ABSTRACTStents made of stainless steel are usually permanently placed in the treated area even after recovering from the disease which can cause problems like in-stent restenosis and thrombosis. A biodegradable stent temporarily opens vessels for remodeling and afterward, it is absorbed. Magnesium is suitable for such application, however, it is limited by its high corrosion rate. Especially iron negatively affects corrosion properties. Manganese as an alloying element can trap iron impurities. In this work, AM50 magnesium alloy was studied in the form of wires. The aim was to find main connections between microstructure, mechanical and corrosion properties of presented materials and compare them with advanced magnesium alloys containing rare earth elements. Studied AM50 is characterized by the tensile yield strength of 258 MPa and elongation of 14%. The reasonable corrosion rate of 1.24 mm/y and good cytocompatibility of AM50 alloy predetermine this alloy as a suitable material for stent application.

Engineering prediction of fatigue strength for AM50 magnesium alloys

In the automotive industry, the use of magnesium alloys is increasing due to their low weight and relative good mechanical properties. However, the variable loading conditions require knowing the fatigue properties of these alloys. The paper presents original results for fatigue strength of AM50 magnesium alloy used for die casting of steering wheels. Three different types of specimens were tested in rotating bending in order to determine the fatigue strength of AM50 magnesium alloy. The effects of stress concentration and surface finishing are also investigated.The fatigue strength at 106 cycles was obtained 55.85 MPa for un-notched finished specimen and decrease for as casted R-radius specimens with 25%, respectively with 61.2% for V-notch specimens.Finally, correlations of fatigue strength with tensile strength and HV hardness are proposed, which are helpful in the design stage of magnesium alloy components.

Effect of Gd Addition on Corrosion Behavior of AM60 Magnesium Alloy

Effect of Gd Addition on Corrosion Behavior of AM60 Magnesium Alloy

An influence of impact energy on magnesium alloy behaviour

The paper reports experimental results describing behaviour of the AM60 magnesium alloy under impact test. The material was examined at energy in the range from 170 to 690 J, using impact tower with the projectile of conical shape. Results are presented in a form of variations of accumulated energy, force, projectile velocity and its displacement versus time. The characteristic features appearing in courses of force and accumulated energy are illustrated. Fractography and microstructure of damage zones for distinguishing the alloy degradation are shown. The fracture regions of the material examined are represented by cracks and plug-shaped deformation.

Influence of glycerol on plasma electrolytic oxidation coatings evolution and on corrosion behaviour of coated AM50 magnesium alloy

PEO coatings were obtained from base silicate electrolyte (bPEO) and glycerol added silicate electrolytes (gPEO) for different processing times. PEO coatings’ evolution and their corrosion behavior were systematically studied as a function of PEO processing time. Smaller maximum pore size and higher pore density have been discerned for gPEO compared to bPEO for all the PEO processing time. Glycerol addition resulted in reduced coating thickness, promoted periclase, MgO, formation and suppressed forsterite, Mg2SiO4, amorphization. From electrochemical impedance spectroscopy study, it was found that gPEO had better corrosion resistance as compared to bPEO.

Comparative studies on the structure and properties of rapidly solidified and conventionally cast AM60 magnesium alloys

The flow stress and work-hardening of rapidly solidified, (RS), and conventionally cast, (IM), AM60 magnesium alloy has been investigated under conditions of uniaxial tension and compression at 4 K, 78 K and 298 K. Rapid solidification combined with plastic consolidation through hot extrusion permit to obtain the alloy with reduced grain size and refined intermetallic particles, which otherwise precipitate in the form of large aggregates in commercial alloys. RS alloy exhibit higher strength and better ductility than IM material. Enhancement of mechanical properties of RS alloy is discussed in terms of the features of material's microstructure. The analysis of work-hardening reveals that independently of deformation temperature and deformation mode, RS alloy shows a lower capacity of defects storage in the substructure. This behaviour is attributed to reduced non-basal slip and forest hardening and enhanced recovery of basal dislocations at grain boundaries in fine-grained RS alloy. Grain boundary sliding does not play an important role in the deformation process. Fracture of the alloys is particle-stimulated and occurs by nucleation and growth of voids around second phase particles. Refining particles by rapid solidification lead to the better ductility of RS alloy irrespective of deformation temperature.

Microstructure, Texture, and Mechanical Properties of AM60 Magnesium Alloy Processed by Extrusion and Multidirectional Forging

In the present paper, multidirectional forging (MDF), as a severe plastic deformation process, was carried out on an extruded AM60 magnesium alloy. The microstructure, texture, and mechanical properties of the MDFed samples were examined. Microstructural findings indicated that the grain size of the alloy decreased from 10.2 to 3.7 µm after six MDF passes, carried out at a constant temperature of 220 °C. Textural studies revealed that after six MDF passes, the fiber texture of the extruded material was transformed to another texture, in which the basal planes tend to rotate toward 45o to the transverse direction. Shear punch testing (SPT) was employed to assess the shear yield stress (SYS) and ultimate shear strength (USS) at room temperature. Both SYS and USS were enhanced after two MDF passes, but decreased in the next pressing stages, despite developing finer grains at higher levels of imposed strain. The observed drop in strength is ascribed to texture softening that counterbalances the grain refinement strengthening effects. The variation in average microhardness values after different passes of MDF showed the trend that was in concurrence with the rise and fall of the SPT results. Finally, the changes in mechanical properties were discussed, based on the microstructural and textural findings.

Protective Performance of Plasma-Enhanced Chemical Vapor-Deposited Ethyl Cyclohexane Coating on Magnesium Alloys

In the present investigation, plasma-polymerized ethyl cyclohexane (ECH) coatings were deposited onto AZ31 and AM50 magnesium (Mg) alloys using plasma-enhanced chemical vapor deposition. The influences of deposition time on the coating formation, surface morphology, chemical composition and electrochemical corrosion behavior were investigated. The coating deposition was confirmed by infrared spectroscopy (FT-IR), and the thickness was measured using a scanning electron microscope. Energy-dispersive x-ray analysis revealed an increase in carbon and a decrease in Mg concentrations as the coating duration was increased. Electrochemical impedance spectroscopy (EIS) results confirmed an improvement in the corrosion resistance of AZ31 and AM50 alloys due to ECH coatings in the presence of a 3.5 wt.% NaCl solution. Further, equivalent circuit curve fitting analysis of the EIS results indicated an increase in charge transfer resistance (Rct) values with longer coating durations. These results confirmed the protecting ability of ECH coatings against corrosive ion attack, which was also substantiated by the surface morphologies after corrosion. Impedance values decreased as the duration of exposure in a NaCl solution increased, and the coating prepared using a 30-min ECH deposition exhibited better protection properties.

Effect of pH value on the corrosion and corrosion fatigue behavior of AM60 magnesium alloy

Abstract

Effect of Laser Welding Parameters on Porosity of Welds in Cast Magnesium Alloy AM50

Pores in the weld metal lower the mechanical properties of the weld. It is therefore important to understand the pore formation mechanisms and find procedures that could reduce porosity. This study ...

Research of the Cutting Possibility of Magnesium Alloys with Abrasive Diamond Wire Saw

Abstract Wire saw technology is a method that works great in industrial applications – it is a dominant method in the production of silicon wafers. But almost all kinds of brittle materials (ceramics, rocks, meteorite and minerals or wood) can be cut using wire saw. Question, this article will try to answer is whether this is also applicable to magnesion alloys? Article presents selected problems from an area of abrasive treatment of magnesium alloys. This includes effects of research, concerning possibilities of application of abrasive diamond wire in the process of cutting magnesium alloys AM60 and AZ91 as well as results concerning surface quality obtained after cutting with the abrasive diamond wire German Company HK Präzisionstechnik.

Numerical study of the behavior of magnesium alloy AM50 in tensile and torsional loadings

In this work, a numerical simulation of the behavior of the magnesium alloy AM50 in tension and torsion is performed. Preliminary experimental procedures were carried out in order to determine the material characteristics and the stress–strain response. Based on the experimental data, three material models were developed: linear elastic with isotropic plasticity, linear elastic with Johnson–Cook hardening and the Ramberg–Osgood model and their accuracy and computational time were investigated.

Workability Characteristics and Deformation Mechanisms of Die-Cast AM60 and AZ91 Magnesium Alloys: Correlation with Processing Maps

Thermo-mechanical deformation behavior of the die-cast AM60 and AZ91 alloys was assessed by performing uniaxial compression tests on Gleeble 3800 simulator under different temperatures and strain rate conditions. Low-temperature deformation behavior of both alloys was accessed at 25, 100, and 150 °C, at the strain rates of 0.1 and 1 s−1. Processing maps at a true strain of 0.5 were generated to study the intrinsic hot workability of AM60 and AZ91 alloys. Optimum processing windows were identified, and the evolution of microstructures and textures was correlated with the imposed deformation conditions. The processing map for the AM60 alloy exhibited three dynamic recrystallization (DRX) domains in the ranges: (1) 320-400 °C and 0.2-1.5 s−1, (1A) 300-325 °C and 0.1-0.2 s−1, and (2) 360-400 °C and 3-5 s−1. In Domain 1, DRX occurred predominantly by pyramidal slip and recovery mechanisms by cross-slip as confirmed by the randomized textures. Deformation in Domain 1A is by the combination of basal and prismatic slip. In Domain 2, dynamic recovery was a softening mechanism controlled by the climb. The processing map for AZ91 alloy exhibited two DRX domains in the ranges: (1) 260-310 °C and 0.1-0.5 s−1 and (2) 325-350 °C and 0.8-3 s−1. The rate-controlling mechanism was climb by lattice self-diffusion in Domain 1 and by grain boundary self-diffusion in Domain 2. Both alloys exhibited flow instability at 200 and 250 °C, and therefore, they were unsuitable for processing at these temperatures.

The wear characteristics of CeO2 containing nanocomposite coating made by aluminate-based PEO on AM 50 magnesium alloy

This study examined the influence of CeO2 nanoparticles on the wear characteristics of aluminate-based PEO coatings formed on the AM50 magnesium alloy, which was developed for the automotive industry. Sliding wear assessments were conducted on a ball-on-disk tribometer at 2 N, 5 N and 10 N loads (against an AISI 52100 steel ball). It was found that the wear characteristics were greatly affected by the addition of CeO2 nanoparticles, especially under intermediate and high loads. The coatings with and without CeO2 remained intact during the sliding test at 2 N. Under an intermediate load of 5 N, the coating treated in the absence of CeO2 failed, while the one made in the presence of CeO2 offered superior wear resistance without any signs of wear failure. Under the 10 N load, the CeO2-free coating was completely removed and the substrate emerged, which was mainly due to a combined adhesive–abrasive wear damage mechanism; in contrast, the CeO2-containing coating (PEO-CeO2) offered much superior wear resistance to the Mg alloy, which was consistent with the friction coefficient data. SEM-EDS analysis of the worn surface of the steel balls also indicated that the transfer of the coating fragments to the ball surface was more intensive for the nanoparticle-free coating, as compared to that observed for the PEO-CeO2 coating. Also, the appearance of some deep scoring in the worn surface of the balls could be considered as a result of the three-body abrasive wear. The superior wear resistance of the CeO2 embedded nanocomposite coating could be mainly attributed to its lower porosity, lower roughness, and higher hardness.

Effects of Mg–Zn–Y quasicrystal addition on the microstructures, mechanical performances and corrosion behaviors of as-cast AM60 magnesium alloy

In this work, the as-cast Mg–50Zn–5Y (mass fraction) master alloy containing Mg42Zn50Y8 (mole fraction) icosahedral quasicrystal phase (I-phase) was prepared. The influences of addition amount of the Mg–50Zn–5Y master alloy on the microstructure, mechanical performances and corrosion properties of AM60 alloys were studied, aiming to investigate the structure-activity relationship for optimizing the microstructures and properties of AM60 alloys. The results indicated that the continuous reticulation structure could be broken and the precipitated phases could be significantly refined by adding the Mg–50Zn–5Y quasicrystal master alloy. The quasicrystal-reinforced AM60 alloys exhibited better mechanical properties and corrosion resistance than unmodified one. The modified AM60 alloy with 6 wt% of the Mg–50Zn–5Y quasicrystal master alloy had the optimal mechanical performances and corrosion resistance such as a Brinell hardness of 74 HB (increased by 37.0%), an ultimate tensile strength of 205 MPa (increased by 24.3%), a yield strength of 99 MPa (increased by 32.0%) as well as a corrosion rate of 1.35 × 10−2 mm·year−1 (decreased by 93.1%). The broken of the continuous reticulation structure and the refinement of the precipitated phases were responsible for the improvement of mechanical performances and corrosion resistance.

Deformation Behavior of AM30 Magnesium Alloy

In this study, deformation behavior of AM30 magnesium alloy is investigated in the hot working regime and empirical relations are developed. Compression tests were performed in the 0.001-10 s−1 strain rate range and 423-623 K temperature range to obtain the mechanical properties. The compression curves were fitted using two approaches, viz. piecewise linear fitting and a Johnson–Cook type relation. Piecewise linear fit is found to be appropriate for describing the mechanical behavior in the dynamic recrystallization (DRX) regime as compared to the proposed Johnson–Cook type relation. The Johnson–Cook type model is not able to capture the essential feature of DRX, particularly at high strain rates.